pasting large multiline text is extremelly slow

# Environment

Windows Terminal Preview v1.6.10272.0 on windows 10 20h2

# Steps to reproduce

1. start wt with cmd
2. launch neovim in terminal mode (no gui)
3. enter insert mode with
4. paste a large text, like 200k of json
5. you get the warning about large text being pasted, accept it
6. wait....I had to kill wt, not sure how long I would need to wait (many minutes?)

# Expected behavior

the text gets pasted instantly

# Actual behavior

you have to wait a lot.

I tried pasting the same text in neovim-qt (the official GUI version of neovim) and the text gets inserted instantly.

I understand pasting large text would be weird in normal terminal usage, but when you are using wt to host neovim it is a legit use case.

Reproduce this on Windows Terminal Preview with cmd, Neovim in terminal mode, and a 200k JSON paste after accepting the large-text warning. Compare the behavior with neovim-qt and investigate the paste path; done means the large multiline text is inserted without the multi-minute delay.

Written by the indexing model from the issue text.